This proposal is for the extension of our studies on the crystal and molecular structures of the nucleic acid constituents, their analogues, amino glycosyl nucleoside antibiotics, metal-phosphate and metal-nucleotide complexes. Crystallization and structural studies of di-, tri- and oligo-nucleotides will be given special attention to close the gap between our extensive structural knowledge of the monomeric nucleoside and nucleotides on the one hand, and the macromolecular fibrous helical structures and more recently the single crystal structures of two crystal polymorphs of yeast tRNA Phe on the other. The main technique used will be x-ray diffraction. The studies will furnish additional stereochemical data on the glycosyl torsion, the sugar pucker, the exocyclic C4'-C57 torsion, and most importantly information on the internucleotide P-O ester bond torsions and their correlation to base stacking patterns. Such information is central to our exploration of the skeletal bond conformations in the loops, bends and bulges of the sugar-phosphate-sugar backbone folds of polynucleotides and nucleic acids. Energy calculations will be used to extract information on the relative importance of the various conformational states and neighbor bond correlations of oligonucleotides. The structural knowledge sought in this proposal will form an important basis in furthering our understanding of the structure-dynamics and structure-function relationships of the molecules of the genetic system.